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    Subject[PATCH 5.4 027/158] sctp: change to hold/put transport for proto_unreach_timer
    Date
    From: Xin Long <lucien.xin@gmail.com>

    [ Upstream commit 057a10fa1f73d745c8e69aa54ab147715f5630ae ]

    A call trace was found in Hangbin's Codenomicon testing with debug kernel:

    [ 2615.981988] ODEBUG: free active (active state 0) object type: timer_list hint: sctp_generate_proto_unreach_event+0x0/0x3a0 [sctp]
    [ 2615.995050] WARNING: CPU: 17 PID: 0 at lib/debugobjects.c:328 debug_print_object+0x199/0x2b0
    [ 2616.095934] RIP: 0010:debug_print_object+0x199/0x2b0
    [ 2616.191533] Call Trace:
    [ 2616.194265] <IRQ>
    [ 2616.202068] debug_check_no_obj_freed+0x25e/0x3f0
    [ 2616.207336] slab_free_freelist_hook+0xeb/0x140
    [ 2616.220971] kfree+0xd6/0x2c0
    [ 2616.224293] rcu_do_batch+0x3bd/0xc70
    [ 2616.243096] rcu_core+0x8b9/0xd00
    [ 2616.256065] __do_softirq+0x23d/0xacd
    [ 2616.260166] irq_exit+0x236/0x2a0
    [ 2616.263879] smp_apic_timer_interrupt+0x18d/0x620
    [ 2616.269138] apic_timer_interrupt+0xf/0x20
    [ 2616.273711] </IRQ>

    This is because it holds asoc when transport->proto_unreach_timer starts
    and puts asoc when the timer stops, and without holding transport the
    transport could be freed when the timer is still running.

    So fix it by holding/putting transport instead for proto_unreach_timer
    in transport, just like other timers in transport.

    v1->v2:
    - Also use sctp_transport_put() for the "out_unlock:" path in
    sctp_generate_proto_unreach_event(), as Marcelo noticed.

    Fixes: 50b5d6ad6382 ("sctp: Fix a race between ICMP protocol unreachable and connect()")
    Reported-by: Hangbin Liu <liuhangbin@gmail.com>
    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Link: https://lore.kernel.org/r/102788809b554958b13b95d33440f5448113b8d6.1605331373.git.lucien.xin@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/sctp/input.c | 4 ++--
    net/sctp/sm_sideeffect.c | 4 ++--
    net/sctp/transport.c | 2 +-
    3 files changed, 5 insertions(+), 5 deletions(-)

    --- a/net/sctp/input.c
    +++ b/net/sctp/input.c
    @@ -449,7 +449,7 @@ void sctp_icmp_proto_unreachable(struct
    else {
    if (!mod_timer(&t->proto_unreach_timer,
    jiffies + (HZ/20)))
    - sctp_association_hold(asoc);
    + sctp_transport_hold(t);
    }
    } else {
    struct net *net = sock_net(sk);
    @@ -458,7 +458,7 @@ void sctp_icmp_proto_unreachable(struct
    "encountered!\n", __func__);

    if (del_timer(&t->proto_unreach_timer))
    - sctp_association_put(asoc);
    + sctp_transport_put(t);

    sctp_do_sm(net, SCTP_EVENT_T_OTHER,
    SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
    --- a/net/sctp/sm_sideeffect.c
    +++ b/net/sctp/sm_sideeffect.c
    @@ -419,7 +419,7 @@ void sctp_generate_proto_unreach_event(s
    /* Try again later. */
    if (!mod_timer(&transport->proto_unreach_timer,
    jiffies + (HZ/20)))
    - sctp_association_hold(asoc);
    + sctp_transport_hold(transport);
    goto out_unlock;
    }

    @@ -435,7 +435,7 @@ void sctp_generate_proto_unreach_event(s

    out_unlock:
    bh_unlock_sock(sk);
    - sctp_association_put(asoc);
    + sctp_transport_put(transport);
    }

    /* Handle the timeout of the RE-CONFIG timer. */
    --- a/net/sctp/transport.c
    +++ b/net/sctp/transport.c
    @@ -133,7 +133,7 @@ void sctp_transport_free(struct sctp_tra

    /* Delete the ICMP proto unreachable timer if it's active. */
    if (del_timer(&transport->proto_unreach_timer))
    - sctp_association_put(transport->asoc);
    + sctp_transport_put(transport);

    sctp_transport_put(transport);
    }

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